This disclosure relates to geophysical exploration, more specifically it relates to land seismic survey methods and systems.
Seismic exploration involves surveying subterranean geological formations for hydrocarbon deposits. A survey typically involves deploying seismic source(s) and seismic sensors at predetermined locations. The sources generate seismic waves, which propagate into the geological formations creating pressure changes and vibrations along their way. Changes in elastic properties of the geological formation scatter the seismic waves, changing their direction of propagation and other properties. Part of the energy emitted by the sources reaches the seismic sensors. In response to the detected seismic events, the sensors generate electrical signals to produce seismic data. Analysis of the seismic data can then indicate the presence or absence of probable locations of hydrocarbon deposits.
Some surveys are known as “marine” surveys because they are conducted in marine environments. However, “marine” surveys may not only be conducted in saltwater environments, but also in fresh and brackish waters. In one type of marine survey, called a “towed-array” survey, an array of seismic sensor-containing streamers and sources is towed behind a survey vessel. In one type of survey, called a “marine vertical seismic profile (marine VSP)” survey, an array of sensors is deployed in a borehole and the seismic source is either moving (e.g. towed behind a vessel) or stationary (e.g. suspended from a structure such has a drilling rig). In one type of marine survey, incorporating both hydrophones and geophones, called an “Ocean Bottom Cable (OBC)” survey, sensors are laid on the seabed. In another type of marine survey, the sensors are deployed in other ways and the seismic source is deployed in the water in some way, where the sensors or sources can be either moving or stationary. Other surveys are known as “land” surveys because they are conducted on land environments. Land surveys may use dynamite or seismic vibrators as sources. Arrays of seismic sensor-containing cables are laid on the ground to receive seismic signals. The seismic signals may be converted, digitized, stored or transmitted by sensors to data storage and/or processing facilities nearby, e.g. a recording truck. Land surveys may also use wireless receivers to avoid the limitations of cables. Seismic surveys may be conducted in areas between land and sea, which is referred to as the “transition zone”.
Marine surveys and land surveys are very different due to the different operation environments. For example, marine-based measurements are typically based on pressure variations, whereas land-based techniques are typically based on particle motion. Accordingly, the equipment or methods used in land surveys are generally different from those used in marine surveys.
The following references may provide relevant background knowledge. They are incorporated herein by reference for all purposes:    Muyzert: 53.0099-US, US20100195439, Seismic acquisition system and technique    Vassallo, M, Özbek, A., Özdemir, A., K. Eggenberger, 2010. Geophysics, 75, WB53-WB67.    Bagaini, 2010. Acquisition and processing of simultaneous vibroseis data, Geophysical Prospecting, Vol. 58, 81-99.    Robertsson, J. O. A., van Manen, D-J., Halliday, D., Laws, R., 2008. Seismic data acquisition and source-side derivatives generation and application. U.S. Pat. No. 7,492,665 B2.    Broggini, F., Halliday, D., Kragh, E., 2011, The contribution of the spatial derivatives to surface-wave interferometry, SEG Technical Program Expanded Abstracts, 30 (1) pp. 3804-3808.    Fokkema, J. T., van den Berg, 1993. Seismic Applications of Acoustic Reciprocity, Elsevier, Amsterdam.